DiscoveryService (Hazelcast Root 3.12.12 API)

All Known Implementing Classes:

DefaultDiscoveryService, PredefinedDiscoveryService
```
public interface DiscoveryService
```
The DiscoveryService interface defines the basic entry point into the Discovery SPI implementation. If not overridden explicitly the Hazelcast internal DefaultDiscoveryService implementation is used. A DiscoveryService somehow finds available DiscoveryStrategys inside the classpath and manages their activation or deactivation status.
This interface is used by system integrators, integrating Hazelcast into their own frameworks or environments, are free to extend or exchange the default implementation based on their needs and requirements.
Only enabled providers are expected to discover nodes but, depending on the DiscoveryService implementation, multiple DiscoveryStrategys might be enabled at the same time (e.g. TCP-IP Joiner with well known addresses and Cloud discovery).

Since:

3.6

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`void`	`destroy()` The `start` method is called on system startup to implement simple lifecycle management.
`Map<String,Object>`	`discoverLocalMetadata()` Returns a map with discovered metadata provided by the runtime environment.
`Iterable<DiscoveryNode>`	`discoverNodes()` Returns a discovered and filtered, if a `NodeFilter` is setup, set of discovered nodes to connect to.
`void`	`start()` The `start` method is called on system startup to implement simple lifecycle management.

- Method Detail
  - start
```
void start()
```
    The start method is called on system startup to implement simple lifecycle management. This method is expected to call DiscoveryStrategy.start() on all discovered and start up strategies.
  - discoverNodes
```
Iterable<DiscoveryNode> discoverNodes()
```
    Returns a discovered and filtered, if a NodeFilter is setup, set of discovered nodes to connect to.
    
    Returns:
    
    a set of discovered and filtered nodes
  - destroy
```
void destroy()
```
    The start method is called on system startup to implement simple lifecycle management. This method is expected to call DiscoveryStrategy.destroy() on all discovered and destroy strategies before the service itself will be destroyed.
  - discoverLocalMetadata
```
Map<String,Object> discoverLocalMetadata()
```
    Returns a map with discovered metadata provided by the runtime environment. Those information may include, but are not limited, to location information like datacenter, rack, host, node name or additional tags to be used for custom purpose.
    Information discovered from this method are shaded into the Members attributes. Existing attributes will not be overridden, that way local attribute configuration overrides provided metadata.
    The default implementation provides an empty map with no further metadata configured. Returning null is not permitted and will most probably result in an NullPointerException inside the cluster system.
    
    Returns:
    
    a map of discovered metadata as provided by the runtime environment
    
    Since:
    
    3.7

Interface DiscoveryService

Method Summary

Method Detail

start

discoverNodes

destroy

discoverLocalMetadata